Of course, sometimes the person doing this wants everyone, particularly their victim, to know it was done very deliberately, and will communicate this by issuing an insincere or flat-out sarcastic apology. However, this also means that people can, on occasion, do something generally mean-spirited to someone else in public, and potentially get away with it if it appears to have been a mistake. Hence, when someone accidentally spills a drink, or steps on a foot, or knocks something over, most people are willing to forgive and forget if an apology is given. Most people are aware of this, and recognize that we are all prone to the occasional act of clumsiness and carelessness.